1. Technical Field
The present invention relates to technology for protecting rights to digital content, and more particularly to a technique for issuing and managing electronic tickets.
2. Related Art
In recent years, various types of digital content, such as image data, video data, document data, music data, and game and other programs, have been supplied from a variety of content providers to users. When such digital content is supplied, a digital right management (DRM) technology is employed for protecting rights, such as a copyright and the like, of a content provider.
A typical application example of a DRM technology is a system using electronic tickets. In this system, digital content is distributed to users in a state where usage restrictions on the digital content are defined by means of an encryption technique. Defining these types of usage restrictions is also referred to as “encapsulation.” In order to utilize encapsulated digital content (hereinafter simply referred to as a “capsule”), a user should separately obtain an electronic ticket which contains information such as a key necessary for removing the usage restrictions. An electronic ticket is sometimes referred to as a license.
As one electronic ticket issuing and managing scheme, there has been known a system using an access control list. In this system, a usage condition for an individual content item is previously registered for each user in the access control list. When an electronic ticket for a content item is requested from a user, a usage condition for the content item having been specified to the user is obtained in the access control list, and an electronic ticket matching the obtained usage condition is issued.